1. Field of the invention
The present invention relates to the field of implement-mounting fixtures.
2. Background of the Prior Art
Implements, of which farm implements are one example, are used to plow, plant crops, haul materials, and perform a variety of other useful tasks. A work machine carries, deploys, and sometimes powers the implement. Trucks, tractors, all-terrain vehicles (ATVs), maintenance vehicles, and the like are examples of work machines available that typically use implements.
An implement-mounting device is a structure forming a part of an implement that allows the implement to be mounted for use on a work machine.
A work machine is usually supplied with a structure called an implement attachment unit compatible with implement-mounting devices. This allows a variety of implements to be mounted on a work machine in a similar way. An implement attachment unit and a compatible implement-mounting device will be collectively referred to hereafter as a mounting interface.
The square tunnel hitch receiver for pulling trailers and other wheeled implements is a type of implement attachment unit that is now relatively standardized. A bracket attaches a square box beam to the rear or front of the work machine with the box beam tunnel approximately parallel to the work machine centerline. A square hitch bar sized to fit closely within the tunnel has a flat, horizontal plate that projects from the end of the square bar. Aligned holes in the box beam and hitch bar allow a pin to strongly hold the bar in the tunnel. Removing the pin allows the hitch bar removal to prevent the hitch bar from damaging other vehicles, and allows replacement by other hitch bars. The standard trailer hitch attaches to a trailer ball bolted through a vertical hole in the plate.
The square tunnel hitch receiver is suitable for pulling trailers and other wheeled implements but is usually unsuitable for other types of implements. For example, many types of implements, such as scrapers, mowers, etc. must be lifted from the ground during use and transporting.
A problem with many prior art mounting interfaces that can attach non-trailer type implements to work machines is that they often are unique or proprietary. This results in an implement-mounting device compatible with one type of work machine, but incompatible with other work machines. Other mounting interfaces require bolting at multiple points to attach an implement to the work machine, which is inconvenient and time-consuming.
The three-point hitch is an existing design for a mounting interface. The implement attachment unit of a three-point hitch comprises a central upper arm carried on to the work machine and two lower outboard arms. The upper arm attaches to an upper hitch point forming a part of the implement-mounting device. The two lower arms attach to two lower outboard points on the implement forming a further part of the implement-mounting device.
Typically, the two lower arms are powered to rotate upwards to lift the implement away from the ground. Gravity lowers the implement to ride across the ground when the two lower arms are rotated downward. Where necessary to properly operate an implement such as an aerator or scraper, the lower arms can be powered to force the implement into the ground as well. The upper arm prevents the implement from tilting forward or backward onto the ground when lifted by the lower arms.
The three-point hitch has been in use for 60 years for farm tractors, and has become a de facto standard for tractor mounting interfaces. A detached implement is attached to a tractor having a compatible three-point hitch type implement attachment unit by attaching the three bars of the implement attachment unit to the implement-mounting device on the implement.
Of course, the implement attachment unit of a three-point hitch must be compatible with the implement-mounting device of an implement, to mount that implement. Further, many different types of three-point hitch implement interfaces exist that are incompatible with each other. Thus, one problem with existing three-point hitches as well as other mounting interfaces, is that of incompatibility among manufacturers' product lines.